Turbine rotor with ceramic blades



July 6, 1954 C. SCHGRNER TURBINE ROTOR WITH CERAMIC BLADES Filed Sept. 2, 1949 INVENTOR CHRISTIAN Scu'mvse ATTORNEYS Patented July 6, 1954 TURBINE ROTOR WITH CERAMIC BLADES Christian Schiirner, Augsburg, Germany, assignor to Maschinenfabril; Augsburg-Nurnberg A. G., Augsburg, Germany, a corporation of Germany Application SeptemberZ, 1949, Serial No. 113,720

Claims priority, application Germany October 1, 1948 7 Claims.

elongations of the ceramic material and of the steel are designed as oppositely directed double wedge surfaces whose planes intersect in a concentric-line.

As is well known, the rule of the coinciding wedge surface applies with theoretical accuracy only in case of a certain course of the temperature field. The deviations from these theoretical conditions, caused, e. g., by the inaccuracies involved in determining the heat transmission at the contact surfaces of ceramic material and steel or by the heating and'cooling phenomena during the start and the stoppage and as a result of any changes of the operating conditions of the turbine cannot be considered in the computation with such an accuracy that no additional constraining forces would be produced. V

It is the object ofthe present invention to provide means by which such constraining forcesca-n be avoided irrespectiveof the unavoidable inaccuracies of the computation.

With this object in view according to the present invention the'outer contact surfaces are designed in a way to permit elasticldeformation so that said surfaces act like plate springs following the changes caused in the blade seat under action of the centrifugal force or different heat elongations and thereby maintaining always a reliableseat of the root of the blade.

Since the ceramic material is very sensitive to vibrations, there should be no play between the pairs of wedge surfaces and the root of the blade. On the other hand, in order to introduce the root of the blade into the closed annular groove through the leading-in gap, a larger play will be required between the seating surfaces in the direction of the axis of the blade, so as to avoid jamming, canting or even damages of the blades by the assembling.

In order to reconcile these two contradicting requirements, according to a further feature of the invention-one of the outer wedge-shaped seating surfaces of the steel rotor is detachably mounted on the rim of the rotor and secured thereto only after the blades have been introduced into the rimof the rotor.

The invention will be better understood by reference to the following detailed description in connection with the accompanying drawing showing by way of example and purely schematically one embodiment of the invention, in a fragmentary axial section through the rim of the rotor.

Referring now to the drawing, it will be seen that the root 2 of a ceramic rotor blade I is seated in a closed annular groove 3 of a steel rotor 4. The root of the blade and the annular groove are provided with double-cone seating surfaces 5a, 5b, or 6a, @b, respectively, whose generatrices intersect in a common point 0 or, strictly speaking, in a concentric line 0. The left hand outer counterseating surface 6a is formed as a thin-walled, elastically deformable or resilient annular extension '5 of the rim of the rotor while the corresponding opposite counterseating surface 6a at the right hand side consists of a separate ring I 0 yielding elastically in operation and being secured to the rotor rim after the introduction of the blades, e. g., bywelding.

After the blades have been engaged in the annular groove, which operation is substantially facilitated by the fact that the gap at the right hand upper corner of the annular groove for the blades is still open at that time, this gap is closed by applying the ring I 3, whose conical seating surface ta tightly engages the companion outer seating surface 61) of the root of the blade. Since the two outer seating surfaces 6a of the rotor are elastically deformable, they are enabled to compensate potential thermal constraining forces and to ensure a tight fit without play of the root of the blade by utilizing the centrifugal effects and thermal deformations of their carrier elements.

While the invention has been described in detail with respect to certain now preferred examples and embodiments of the invention it will be understood by those skilled in the art after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention and it isintended therefore, to cover all such changes and modifications in the appended claims:

Having thus described my invention, I claim as new and desire to secure by Letters Patent:

1. A gas turbine adapted for high temperature operation comprising a steel rotor, ceramic blades mounted radially around the rim of said rotor with the inner end of said blades disposed toward the axis of said rotor, a first pair of seating surfaces at the inner ends of'said blades beveled in the direction from the axis of said blades toward said inner end, a pair of correspondingly beveled seating surfaces in said rotor for engaging said first pair of surfaces on said blades to resist centrifugal force components, a second pair of seating surfaces on said blade outwardly of said first pair and adjacent said rotor rim, said second pair of seating surfaces being beveled in an opposite direction from said first pair, resilient members on said rotor rim adjacent said second pair of seating surfaces, said resilient members having seating surfaces correspondingly beveled to said second pair for engagement therewith to urge said blade outwardly from said rotor, said two pairs of oppositely directed seating surfaces on said blade cooperating with said correspondingly beveled surfaces in said rotor for maintaining firm and substantially vibrationless engagement of said blade in said rotor during thermal expansion and axial movement of said blades with respect to said rotor.

2. A gas turbine adapted for high temperature operation comprising a steel rotor, ceramic blades having thermal expansion characteristics different from said steel rotor and mounted around the rim thereof, grooves in said rotor rim for receiving said blades, a first set of cooperating beveled seating surfaces in said grooves and on said blades at the radially inner ends thereof for engaging said blades in said grooves, said seating surfaces being outwardly inclined toward a radius of said rotor to resist centrifugal force components during operation of said rotor, resilient members on said rotor rim around said grooves, a second set of cooperating seating surfaces on said rotor and said blades beveled in the opposite direction from said first set, said second set of surfaces on said rotor being carried by said resilient members and said resilient members and said second set of surfaces cooperating for maintaining firm engagement of said first set of seating surfaces during different thermal expansions of said steel rotor and said ceramic blades and for maintaining non-rigid but substantially vibrationless engagement of said blade in said grooves during limited axial movement of said blades with respect to said rotor.

3. A gas turbine for high temperature operation comprising in combination a steel rotor, ceramic blades mounted around the rim of said rotor and having thermal expansion characteristics different from said steel rotor, first beveled seating surfaces on said blades at the radially inner ends thereof, correspondingly beveled first seating surfaces in said rotor engaging said first surfaces on said blades, said seating surfaces being outwardly inclined toward a radius of said rotor for resisting centrifugal force components;

second seating surfaces on said blades beveled in the opposite direction from said first surfaces, resilient members on said rotor adjacent said second seating surfaces, said resilient members having seating surfaces correspondingly beveled to said second surfaces on said blade and sin gaging therewith for maintaining firm and substantially vibrationless engagement of said blade in said rotor during the different thermal expansions of said blade and said rotor, at least a portion of said resilient members being detachable from said rotor for assembling and replacing said blades therein.

4. A gas turbine for high temperature operation comprising in combination a steel rotor,

ceramic blades mounted around the rim of said rotor and having thermal expansion characteristics different from said steel rotor, first beveled seating surfaces on said blades at the radially inner ends thereof, correspondingly beveled first seating surfaces in said rotor engaging said first surfaces on said blades, said seating surfaces being outwardly inclined toward a radius of said rotor for resisting centrifugal force components, second seating surfaces on said blades beveled in the opposite direction from said first surfaces, resilient members on said rotor adjacent said second seating surfaces, said resilient members having seating surfaces correspondingly beveled to said second surfaces on said blade and engaging therewith for maintaining firm and substantially vibrationless engagement of said blade in said rotor during the different thermal expansions of said blade and said rotor, said first and second seating surfaces lying in planes which intersect each other at the central longitudinal axis of said blades.

5. A steel rotor for carrying mounted around the rim thereof ceramic turbine blades having different thermal expansion characteristics from said rotor and adapted for use in high temperature gas turbines comprising for each said ceramic blade an annular groove in said rotor rim, beveled seating surfaces in said groove for engaging corresponding beveled seating surfaces on said blade for holding said blade against centrifugal force components developed during oper ation of said rotor and elastically deformable rim portions around said groove, said portions having seating surfaces beveled in a direction opposite to said first mentioned seating surfaces for urging said blade outwardly from said rotor to maintain firm engagement between said first mentioned surfaces on said blade and said rotor during said different thermal expansions.

6. A steel rotor for carrying mounted around the rim thereof ceramic turbine blades having different thermal expansion characteristics from said rotor and adapted for use in high temperature gas turbines comprising for each said ceramic blade an annular groove in said rotor rim, beveled seating surfaces in said groove for engaging corresponding beveled seating surfaces on said blade for holding said blade against centrifugal force components developed during operation of said rotor and elastically deformable rim portions around said groove, said portions having seating surfaces beveled in a direction opposite to said first mentioned seating surfaces for urging said blade outwardly from said rotor to maintain firm engagement between said first mentioned surfaces on said blade and said rotor during said different thermal expansions, at least a part of said elastic portions being detachable from around said groove for assembling and replacing said blades in said rotor.

7. A steel rotor for carrying mounted around the rim thereof ceramic turbine blades having different thermal expansion characteristics from said rotor and adapted for use in high temperature gas turbines comprising for each said ceramic blade an annular groove in said rotor rim, beveled seating surfaces in said groove for engaging corresponding beveled seating surfaces on said blade for holding said blade against centrifugal force components developed during on eration of said rotor and elasticaly deformable rim portions around said groove, said portions having seating surfaces beveled in a direc on opposite to said first mentioned seating surfs for urging said blade outwardly from said rotor to maintain firm engagement between said first mentionedsurfaces on said blade and said rotor during said different thermal expansions, said beveled seating surfaces lying in planes which intersect each other at the central longitudinal axis of said blade when mounted in said groove.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 883,889 Kierser Apr. 7, 1908 2,317,338 Rydmark Apr. 20, 1943 OTHER REFERENCES Serial No. 385,333, Schutte (A. P. C.), published May 25, 1943.

Serial No. 385,334, Schutte (A. P. C.) published May 25, 1943. 

